The present invention relates to solderable terminals and leads, particularly solder clips intended for connection to contact pads on edges of substrates.
Several leads exist in the market in the form of a clip adapted resiliently to engage the edges of a substrate, while a mass of solder is held on the clip adjacent the position of a conductive area or pad on the substrate. Upon heating the substrate/terminal assembly, the solder mass melts and is drawn, usually by capillary action, to the area of contact between the terminal and the substrate conductive area. Examples of such solderable clips are shown in U.S. Pat. Nos. 4,120,558; 4,019,803; 4,203,648; 4,357,069; 4,367,910; 4,592,617; 4,605,278; 4,697,865; 4,728,305; and 4,780,098. Unfortunately, these terminals generally involve complex structures, such as curved fingers or tabs, for forming the lead and holding the solder mass in place until the assembly is heated, requiring specialized tooling and production techniques.
A device disclosed in U.S. Pat. No. 4,900,279 to Dennis partially solves this problem. This devices uses a basically C-shaped clip that is coated on the interior of the C with solder. The substrate is inserted into the interior of the C, bringing the contact pads of the substrate in contact with the solder, which is then melted, forming when re-solidified a mechanical and electrical connection between the clip and the substrate. Unfortunately, when the solder melts, the significant layer of liquid solder between the clip and the substrate create an unstable hold on the substrate. The substrate tends to float or slide around in relation to the clip during this period. This can potentially lead to a solder connection of the clip to an area partially or completely off of its desired contact pad, which may cause a short-circuit to an adjacent, closely spaced contact pad.